Level takes place on a screen

corlenbelspar · Post by **corlenbelspar** » Tue Mar 20, 2012 1:05 am

I was wondering if it were possible on the NES to have a level that takes place on a monitor screen in game. I've included a screenshot below to clarify what I mean.

If not that way, is there any roundabout way to trick the NES to do it in a similar way without using sprites?

Bregalad · Post by **Bregalad** » Tue Mar 20, 2012 1:18 am

This should be possible if the background scrolls in 8/16 pixels increments (or if it doesn't scroll at all) in the horizontal direction at least.
Would not look very good though.

Shiru · Post by **Shiru** » Tue Mar 20, 2012 1:41 am

You can draw the screen in a way that left-right edges aren't visible, so you won't need sprites to cover the edges.

corlenbelspar · Post by **corlenbelspar** » Tue Mar 20, 2012 2:31 am

Would I be able to have the monitor sides as tiles and smooth pixel by pixel scrolling if I made the game not draw the sides of the display of the level itself?

I would be OK with horizontal scroll regions for the top and bottom of the screen where it stays in place and displays the top and bottom of the monitor, but I would prefer if I could have the sides of the monitor in question as well.

Shiru · Post by **Shiru** » Tue Mar 20, 2012 2:37 am

Well, perharps you could make prescrolled graphics for the edges, and update it in the nametable every frame. But in this case you have to deal with attributes clash (can be avoided it if only one palette is used for the whole screen, think sepia style), and scroll update area will be visible, which is certainly looks bad.

corlenbelspar · Post by **corlenbelspar** » Tue Mar 20, 2012 2:39 am

I suppose I'll try it with sprites first and if I get too much sprite flicker I'll just forgo the sides of the monitor.

Post by **tepples** » Tue Mar 20, 2012 5:06 am

A "monitor" screen with borders at left and right like the world map screens in Super Mario Bros. 3? That's certainly possible, though you'll lose a few sprites to drawing the border.

tokumaru · Post by **tokumaru** » Tue Mar 20, 2012 6:19 am

You'd have to use a column of sprites on each side of your "screen" to allow the game window to scroll smoothly, effectively reducing the sprites-per-scanline limit to 6. Also, except for the parts drawn with sprites, the sides of the screen would have to be flat. If those limitations don't bother you, go ahead.

Roth · Post by **Roth** » Tue Mar 20, 2012 9:21 am

Bregalad wrote:This should be possible if the background scrolls in 8/16 pixels increments (or if it doesn't scroll at all) in the horizontal direction at least.
Would not look very good though.

For an idea of what this idea of Bregalad's would look like, here's a vid of something I worked on before:

http://blip.tv/slydogstudios/nes-homebr ... 00-5900509

Note that it's going by tile, so 8 pixels, not 16. The downside here is that each of these separate rows that move all keep the same attributes. This means you would have to move by 16, so moving each column over by two instead of one (16 instead of 8) to keep the attributes aligned. I think this would be too jumpy, personally.

Tokumaru's idea is probably the closest you could get, but as he said, it is very, very limiting also. It might even take too many sprites just trying to cover the sides so as to not leave you with enough to work with. It depends on the design of the overall game, I suppose.

tokumaru · Post by **tokumaru** » Tue Mar 20, 2012 11:03 am

Roth wrote:Tokumaru's idea is probably the closest you could get, but as he said, it is very, very limiting also. It might even take too many sprites just trying to cover the sides so as to not leave you with enough to work with.

I wouldn't use sprites to cover the whole area though... most of it would be background tiles (which means you'd have to clear columns of tiles as the screen scrolls, but if you use an unrolled loop this shouldn't take away a lot of precious VBlank time), the sprites would be there just to mask the transition between the flat area and the game window, which could be off by up to 7 pixels.

Only the areas marked in red would have to be sprites. It's enough to draw some sort of trimming, and if you use 8x16 sprites there will be enough left for the game. There are certainly a number of undesirable limitations, but it might be possible to accommodate them in your design if you really need this effect.

Dwedit · Post by **Dwedit** » Tue Mar 20, 2012 11:22 am

For those keeping count, tokumaru's mockup uses 22 sprites, leaving 42 left for the rest of the game.

Roth · Post by **Roth** » Tue Mar 20, 2012 12:40 pm

tokumaru wrote:
Roth wrote:Tokumaru's idea is probably the closest you could get, but as he said, it is very, very limiting also. It might even take too many sprites just trying to cover the sides so as to not leave you with enough to work with.
I wouldn't use sprites to cover the whole area though... most of it would be background tiles (which means you'd have to clear columns of tiles as the screen scrolls, but if you use an unrolled loop this shouldn't take away a lot of precious VBlank time), the sprites would be there just to mask the transition between the flat area and the game window, which could be off by up to 7 pixels.

Only the areas marked in red would have to be sprites. It's enough to draw some sort of trimming, and if you use 8x16 sprites there will be enough left for the game. There are certainly a number of undesirable limitations, but it might be possible to accommodate them in your design if you really need this effect.

How does that work? I was sitting here thinking it was to cover the sides because the whole middle would be scrolling. Is there some kind of "nametable showing through in another nametable" trick that I don't know of?

Post by **tepples** » Tue Mar 20, 2012 2:02 pm

Whenever the screen scrolls 8 pixels, a blank column would be written at the trailing edge (under the sprite column) and the column of newly visible tiles would be written at the leading edge (under the other sprite column).

tokumaru · Post by **tokumaru** » Tue Mar 20, 2012 2:59 pm

Yeah, no trick. Like tepples said, just as a part of the level is about to appear from below the sprites on the trailing edge when the screen scrolls, that column is blanked out, so it becomes part of the border.

Another limitation I just thought of is that the border color would either have to be color 0 or be present in every palette.

Given all the limitations, I'd consider this for special parts of a game, but not the entire thing.

3gengames · Post by **3gengames** » Tue Mar 20, 2012 3:38 pm

Not to be mean...but...